1. Field of the Invention
The present invention relates to a vibration preventing camera that has a vibration correcting unit to compensate for the vibration of an image that is caused by the vibration of the hands that are supporting the camera.
2. Related Background Art
Conventionally, in a general vibration preventing camera, an image vibration detecting unit that detects the amount of vibration and an image vibration correcting unit that compensates for the vibration of an image are always active while the power to the camera is on.
Because the unit in a conventional vibration preventing camera is constantly in the active state, battery power is wasted.
Further, for photography that involves the use of a self-timer, when an image vibration detecting unit and an image vibration correcting unit are activated after the expiration of the set delay time for a self-timer, the shutter exposure timing is delayed.
With one of proposed conventional correction functions, the detection of the vibration level is begun, for example, at the half-stroke position for the release button, vibration correction that is based on the detection result (i.e., a vibration correction optical system is shifted in a direction that is perpendicular to a light axis) is begun at the full-stroke position for the release button, and the vibration correction, or the vibration detection processing, is halted upon the release of the shutter button. To save power, it is desirable that these vibration correction and detection operations be halted if they are not required.
However, since to halt the vibration correcting process by releasing the shutter button, as is described above, a mechanical detection means (hereinafter means encompasses unit) must be provided that can detect the release of the shutter button, and since a large software capacity is also required for the control process, the manufacturing costs for such cameras are accordingly increased.
As one of the above described vibration correcting units, a unit that shifts a part of a lens system, in consonance with a vibration detection result, in order to prevent image vibration at a film plane is conventionally known.
FIGS. 15, 16A, and 16B are schematic diagrams that depict both a camera that employs a vibration detecting unit and its optical system. In FIG. 15, reference number 61 denotes a camera body; 62, a lens barrel; 63, a rangefinder window; 64, a viewfinder; and 65, a release button.
Angular velocity sensors 66 and 67 are internally provided as vibration detecting means in the camera body 61. With the principal point H of the lens barrel 62 as a reference, the angular velocity sensor 66 detects an angular velocity at which the camera body 61 turns along the Y-axis, while the angular velocity sensor 67 detects an angular velocity at which the camera body 61 turns along the X-axis.
The vibration correction unit employs the data concerning the angular velocities, which are detected by the angular sensors 66 and 67 along the X- and Y-axes, to acquire the direction of image vibration and its velocity relative to a film plane 68.
An optical system of lenses shown in FIGS. 16A and 16B are formed with two zoom lens groups; the first group consists of convex lenses L61 and L62 and the second group is a convex lens L63. A wide-angle optical system is shown in FIG. 16A while a telephoto focal optical system is shown in FIG. 16B.
The convex lens L62 of the first lens group is used as a vibration correcting lens (hereafter referred to as a "vibration correcting lens L62"), and is shifted, in the direction indicated by the arrow A, in consonance with the above described data that reflect the direction and velocity of image vibration at the film plane 68.
The image vibration at the film plane 68 is corrected by selecting the direction and the distance to shift the vibration correcting lens L62.
The convex lens L61 is a focusing lens and is shifted, in the direction indicated by the arrow B, to focus an image. Reference numbers 69A and 69B in FIGS. 16A and 16B denote the sections of a lens shutter 69.
Conventionally, the above described vibration correcting unit initiates vibration detection and vibration correction at the time (1) the exposing process is initiated, (2) the main switch is activated, or (3) the half-stroke position for the release button is reached. Thus, the following problems arise.
When the vibration correction is begun at the same time the exposing process is initiated, sometimes a conventional vibration correcting unit cannot fully compensate for the vibration because of the inertia of the vibration correcting lenses and its driving system.
When a conventional unit begins vibration correction at the time the main switch is activated, or the half-stroke position for the release button is reached, measurement of the light amount and the distance must be performed in addition to the vibration correction. As power consumption is significant, the period of time a battery can be used is not long. Further, the processing ability of a controller must be increased to perform vibration correction.
To resolve these shortcomings, the assignee of the present invention has proposed a vibration correcting unit, in Japanese Patent Application Laid-Open No. 5-134287, that employs vibration control means which initiates a vibration correcting process during the period that begins at the termination of a focusing process by focusing means and ends with the initiation of an exposure process by shutter means.
According to this vibration correcting unit, the vibration control means begins driving the vibration correcting lenses before the exposure process begins, so that the exposure process does not overlap the buildup time for the vibration detecting and correcting processing where the performance is unstable. Therefore, stable vibration correction can be performed while the exposure process is conducted, and the exact correction can be provided.
Since the vibration correcting lenses are driven after the focusing is completed, consumed power is lower than that when the vibration correction is begun at the time of the activation of the main switch or when the half-stroke position for the release button is reached. In addition, as the measurements for the light amount and the distance are also completed, the performance ability of the controller does not have to be increased.
The above described vibration correcting unit is still so designed that the vibration detection and correction are performed after the focusing is terminated and immediately before the exposure process. As well as a conventional unit, this vibration correcting unit cannot correct vibration exactly at which it should be performed: (1) at the same time as the initiation of the exposure, (2) at the time the main switch is activated, and (3) at the time the half-stroke position for the release button is reached. The vibration correcting unit, therefore, still has shortcomings in its ability to provide stable imaging.
It is known that the vibration correcting unit is affected by the inertia of the vibration correcting lenses and its driving system, and that it requires a certain buildup time between the point at which vibration sensors are activated and the point at which they are stabilized.
Regarding the buildup time for the vibration correcting unit for vibration detection and correction, a problem still remains in preventing the initial stage of these processes from overlapping the exposure process. It is currently demanded that an entire processing for a camera, including the actual photographing, be reviewed, and that some countermeasure be provided to ensure that the vibration detection and correction will be performed in a desired state, to ensure that adequate photographing with excellent snapshot performance, in which immediate photographing is enabled, can be provided, and to ensure that a stable image can be acquired.
In the entire processing of a camera including photographing, the replacement of batteries or loading a film results in the photographing in near future. It is desirable that by detecting such information, the preparation for photographing, including the vibration detection and correction, be performed in advance to set the camera on standby. It is necessary to consider this matter.
A camera that reduces red-eye phenomenon is also well known. A camera of this type starts emitting (pre-emitting) light from a red-eye reduction lamp, waits a predetermined time, and then performs a flash exposure with an electronic flash unit. In this manner, as the flash exposure is performed while the pupils of a subject (person) who has been looking at the pre-emitted light are not dilated, the redness in the eyes of the person on a photograph is not outstanding.
Normally, in consonance with the reaching of the full-stroke position for the release button, the above described vibration correcting unit drives the vibration correcting optical system first to the initial position (e.g., a position where the light axis of the vibration correcting optical system corresponds to the light axis of the lens), then shifts it from that position to the position that corresponds to the output of the vibration amount detecting sensor, and performs vibration correction. It is therefore necessary, after the full-stroke position for the release button is reached, that the photographing be delayed at least for the period of time it takes for the vibration correcting optical system to be driven to the original position.
It generally takes from 0.7 to 1 second for the subject to look at the pre-emitted light for the red-eye reduction until the diameter of the pupils reaches the minimum. If no light enters the subject's eyes later, the diameter of the pupils will thereafter gradually increase. To provide a satisfactory red-eye reduction effect, therefore, a standby period of from 0.7 to 1 second is required from the light pre-emittance point until the flash exposure point.
As for a camera that, in consonance with the reaching of the full-stroke position for a release button, drives the lens focusing optical system from its reset position (the withdrawn position) by a predetermined value and performs focusing, as the camera-to-subject distance is shorter, the drive distance for the focusing optical system is increased and the focusing takes more time.
Therefore, the vibration correction function and the red-eye reduction function described above include factors that extend the time between reaching the full-stroke position and the taking of a photograph. If a vibration preventing camera has a red-eye reducing function, pre-emittance of light, focusing, and the operational time of the vibration correcting unit must be considered when the conditions for a flash exposure are established. Otherwise, especially when the camera-to-subject distance is short (the drive distance for the focusing optical system is great), the taking of a photograph is significantly delayed and a good shutter chance is missed. Further, when pre-emittance of light for red-eye reduction is performed by a different lamp than that of an electronic flash unit, the light emittance energy is smaller than that of the electronic flash unit, and thus, as the light emittance period must be extended, the above described shortcomings become more critical.
The applicant of the present invention, therefore, has proposed a vibration preventing camera, in Japanese Patent Application No. 6-11668, wherein the activation of a half-stroke switch is synchronized with the arrival of a shutter release button at a half-stroke position in order to calculate an accurate vibration reference level (.omega.=0), which is employed to calculate the absolute value of an angular vibration velocity for vibration detection.
In this vibration preventing camera, special consideration is given to the operational order for the pre-emittance of light for red-eye reduction, the focusing of lenses, and the processing of the vibration correcting unit to minimize the time period from the point at which a photographic start signal is output until flash exposure is performed, and satisfactory vibration correction and red-eye reduction can be obtained.
When a photographing procedure, such as at the half-stroke of a shutter release button or upon ON/OFF manipulation of a full-stroke switch, is performed, or when a photographing mode, such as a flash exposure mode that is accompanied by red-eye reduction or a self-timer photographing mode, is performed with the above described vibration preventing camera, not only the accuracy in vibration detection but also the accuracy in vibration correction depends on when the vibration correcting unit is activated and how long it is in operation.
Especially, the operation that is performed after the full-stroke switch is turned on by the full-stroke of the shutter release button is not disclosed at all for the above described vibration preventing camera. Countermeasures concerning how the vibration detection and vibration correction are to be performed after the full-stroke switch is turned on must be taken to improve the vibration accuracy detection and correction, and for the performance of the vibration correction.